Fan control unit and method

ABSTRACT

A fan control unit measures the rotating speeds of the first and second fans to calculate the relative work intensities of the two fans. The control unit determines whether a difference between the first work intensity and the second work intensity is within a predetermined range. If the difference between the first work intensity and second work intensity is not in the predetermined range, the control unit adjusts a duty cycle of a pulse signal output to one of the first and second fans to change the rotating speed of one of the first and second fans to bring the difference between the first work intensity and the second work intensity within the predetermined range.

TECHNICAL FIELD

The present disclosure relates to a fan control unit and a fan control method.

DESCRIPTION OF RELATED ART

Two fans may be mounted in a computer to dissipate heat from heat generating sources of the computer. However, when the fans have different working speeds, heated air expelled by the fan working at high speed may flow into the fan working at low speed, which affects the dissipation of heat from the computer.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, all the views are schematic, and like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a block diagram of an exemplary embodiment of a fan control unit connected to a first fan and a second fan, wherein the first fan is connected to a power supply, and the second fan is connected to a motherboard.

FIG. 2 is a flowchart of an exemplary embodiment of a fan control method.

DETAILED DESCRIPTION

The disclosure, including the accompanying drawings in which like references indicate similar elements, is illustrated by way of example and not by way of limitation. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

Referring to the FIG. 1, an embodiment of a fan control unit 10 for a first fan 20 and a second fan 30 is provided. The first fan 20 dissipates heat generated by a power supply 40. The second fan 30 dissipates heat generated by a motherboard 50. The fan control unit 10 includes a first pulse output pin PWM1, a second pulse output pin PWM2, a first speed receiving pin TACH1, and a second speed receiving pin TACH2.

In use, the fan control unit 10 outputs a first pulse signal to the first fan 20 through the first pulse output pin PWM1 to control the first fan 20 to rotate. The control unit 10 outputs a second pulse signal to the second fan 30 through the second pulse output pin PWM2 to control the second fan 30 to rotate. The fan control unit 10 measures the rotating speeds of the first and second fans 20 and 30 respectively through the first and second speed receiving pins TACH1 and TACH2. The user presets and records the maximum possible rotating speed of the first fan 20 and of the second fan 30 in the fan control unit 10.

Referring to FIG. 2, an exemplary embodiment of a fan control method includes the following steps.

In step 1, the fan control unit 10 measures the rotating speed of the first fan 20 through the first speed receiving pin TACH1, and measures the rotating speed of the second fan 30 though the second speed receiving pin TACH2.

In step 2, the fan control unit 10 calculates a relationship between the speed and the maximum possible speed of the first fan 20 (a first work intensity) as a percentage and calculates in a similar manner in relation to the second fan 30 (a second work intensity).

In step 3, the fan control unit 10 determines whether any difference in percentages between the first work intensity and the second work intensity is within a first predetermined range. If the difference in percentages between the first work intensity and the second work intensity is within the first predetermined range, it is assumed that there will be no crossflow or backflow adverse to efficient operation between the first and second fans 20 and 30 and then the procedure ends. If the difference in percentages between the first work intensity and the second work intensity is not within the first predetermined range, the likelihood of crossflowing or backflowing air between the fans increases, thereby adversely affecting the heat-dissipating abilities of the first and second fans 20 and 30, or one of them, and the procedure goes to step 4.

In step 4, the fan control unit 10 adjusts a duty cycle of the pulse signal output to one of the first and second fans 20 and 30, specifically to the fan which reveals the lower work intensity, whether this be first work intensity or a second work intensity. The fan control unit 10 changes the rotating speed of the relevant fan of the fans 20 and 30 to decrease the difference in percentages between the first work intensity of the first fan 20 and the second work intensity of the second fan 30 and bring the difference in percentages within the first predetermined range, and the procedure goes back to step 1. For example, if the first work intensity of the first fan 20 is greater than the second work intensity of the second fan 30, and the difference in percentages between the first work intensity and the second work intensity is not within the first predetermined range, the fan control unit 10 increases the duty cycle of the second pulse signal output to the second fan 30 to increase the rotating speed of the second fan 30, to bring the difference in percentages between the first work intensity of the first fan 20 and the second work intensity of the second fan 30 within the first predetermined range. If the second work intensity is greater than the first work intensity, and the difference in percentage between the first work intensity and the second work intensity is not within the first predetermined range, the fan control unit 10 increases the duty cycle of the first pulse signal output to the first fan 20 to increase the rotating speed of the first fan 20, to bring the difference in percentages between the first work intensity of the first fan 20 and the second work intensity of the second fan 30 within the first predetermined range.

In other embodiments, the fan control unit 10 can directly calculate a difference between the duty cycle of the first pulse signal output to the first fan 20 and the duty cycle of the second pulse signal output to the second fan 30. The fan control unit 10 may determine whether the difference is within or outside a second predetermined range. If the difference between the cycle duties of the first pulse signal and the second pulse signal is outside a second predetermined range, it denotes that the heated air expelled by one of the first and second fans 20 and 30 with high duty cycle will flow into the other one of the first and second fans 20 and 30 with low duty cycle. The fan control unit 10 increases the duty cycle of the other one of the first and second pulse signals output to the other one of the first and second fans 20 and 30 with low high duty cycle to bring the difference between the cycle duties of the first pulse signal and the second pulse signal within the second predetermined range.

Although numerous characteristics and advantages of the embodiments have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in the matters of shape, size, and arrangement of parts within the principles of the embodiments to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A fan control unit to control a first fan and a second fan, comprising: a first pulse output pin connected to the first fan to output a first pulse signal to control the first fan to rotate; a second pulse output pin connected to the second to output a second pulse signal to control the second fan to rotate; a first speed receiving pin connected to the first fan to measure a rotating speed of the first fan; and a second speed receiving pin connected to the second fan to measure a rotating speed of the second fan; wherein the fan control unit records the maximum possible rotating speeds of the first and second fans, the fan control unit measures the rotating speeds of the first and second fans to calculate a first work intensity of the first fan and a second work intensity of the second fan, the first work intensity of the first fan is a relationship between the speed and the maximum possible speed of the first fan as a percentage, the second work intensity of the second fan is a relationship between the speed and the maximum possible speed of the second fan as a percentage, the fan control unit determines whether a difference in percentages between the first work intensity and the second work intensity is within a predetermined range, if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, the fan control unit adjusts a duty cycle of the pulse signal output to one of the first and second fans to change the rotating speed of the corresponding one of the first and second fans to bring the difference in percentages between the first work intensity of the first fan and the second work intensity of the second fan within the predetermined range.
 2. The fan control unit of claim 1, wherein if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, and when the first work intensity is greater than the second work intensity, the fan control unit increases the duty cycle of the second pulse signal output to the second fan to increase the rotating speed of the second fan, to bring the difference in percentages between the first work intensity and the second work intensity within the predetermined ranges.
 3. The fan control unit of claim 1, wherein if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, and when the second work intensity is greater than the first work intensity, the fan control unit increases the duty cycle of the first pulse signal output to the first fan to increase the rotating speed of the first fan, to bring the difference in percentages between the first work intensity and the second work intensity within the predetermined ranges.
 4. A fan control method to control a first fan and a second fan, comprising: measuring rotating speeds of the first and second fans; calculating a first work intensity of the first fan and a second work intensity of the second fan through a fan control unit, wherein the first work intensity of the first fan is a relationship between the speed and the maximum possible speed of the first fan as a percentage, the second work intensity of the second fan is a relationship between the speed and the maximum possible speed of the second fan as a percentage; determining whether a difference in percentage between the first work intensity and the second work intensity is within a predetermined range; and adjusting a duty cycle of a pulse signal output to one of the first fan and second fans to change the rotating speed of the corresponding one of the first and second fans, to bring the difference between the first work intensity and the second work intensity within the predetermined range, if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range.
 5. The fan control method of claim 4, wherein the adjusting step comprises: increasing the duty cycle of the pulse signal output to the second fan to increase the rotating speed of the second fan to bring the difference in percentages between the first and second work intensities within the predetermined range, if the first work intensity is greater than the second work intensity.
 6. The fan control method of claim 4, wherein the adjusting step comprises: increasing the duty cycle of the pulse signal output to the first fan to increase the rotating speed of the first fan to bring the difference in percentages between the first and second work intensities within the predetermined range, if the second work intensity is greater than the first work intensity.
 7. A fan control method to control a first fan and a second fan, comprising: calculating a difference between a duty cycle of a first pulse signal output to the first fan and a duty cycle of a second pulse signal output to the second fan; determining whether the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal is within a predetermined range; and adjusting the duty cycle of a corresponding one of the first and second pulse signals output to one of the first and second fans to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal is not within the predetermined range.
 8. The fan control method of claim 7, wherein the adjusting step comprises: increasing the duty cycle of the second pulse signal to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the duty cycle of the first pulse signal is greater than the duty cycle of the second pulse signal.
 9. The fan control method of claim 7, wherein the adjusting step comprises: increasing the duty cycle of the first pulse signal to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the duty cycle of the second pulse signal is greater than the duty cycle of the first pulse signal. 